This invention relates to an ion thruster which may be used, for example for interplanetary space missions.
A conventional ion thruster comprises a vessel, a cathode unit adjacent to the vessel, and a propellant supplying unit connected to the vessel. The cathode unit comprises a hollow cylindrical cathode. The vessel defines a hollow space with an open end and includes an anode. An electrical potential is supplied between the anode and the vessel.
The cathode unit emits thermoelectrons into the hollow space.
The propellant supplying unit supplies a propellant into the hollow space to form a propellant atmosphere in the hollow space.
The thermoelectrons in the thermal atmosphere are accelerated by the electrical potential between the anode and the cathode and come into collision with the propellant to produce plasma which comprises plasma ions and plasma electrons.
An accelerating unit is placed at the opening. The accelerating unit accelerates only the main plasma ions to form and inject an ion beam through the opening towards space.
Alternatively, plasma may be generated in an inert gas atmosphere using microwaves. The inert gas atmosphere may be attained by introducing an inert gas into a hollow space.
It should be noted, however, in connection with the conventional ion thruster, that the cathode must be preheated before operation so that a quick start is possible. Furthermore it, is difficult to prolong the life of the ion thruster because degradation of the electrodes is unavoidable.